Shen RenFang;Zhao QiGuo;Shen RF;Zhao QG

;Laboratory of Material Cycling in Pedosphere, Institute of Soil Science, Academia Sinica, P.O. Box 821, Nanjing 210008, China.

exchangeable calcium;distribution magnesium fertilizers;potassium fertilizers;calcium fertilizers;application transport processes;leaching calcium magnesium potassium soil fertilizers red soils;nutrients

An experiment was carried out with repacked soil columns to study the leaching process of a red soil derived from sandstone as affected by various fertilization practices. The treatments were CK (as a control), CaCO3, CaSO4, MgCO3, Ca(H2PO4)2, Urea,KCl, multiple (a mixture of the above-mentioned fertilizers), and KNO3. After leaching, soils were sampled from 0.5, 5-10, 10-20, 20-40, and 40-60 cm depths. The results showed that application of Ca, Mg, and K to the bare surface of the soil columns increased exchangeable Ca2+, Mg2+, and K+ in the upper layer of the soil profile correspondingly, the extent depending mainly on the application rates and showing a downward trend. CaCO3, CaSO4, MgCO3, and Ca(H2PO4)2 treatments had little if any effect onmovement of exchangeable K+, while CaCO3, and CaSO4 treatments significantly promoted the downward movement of exchangeable Mg2+ although these two treatments had no obvious effect on leaching losses of Mg. Under urea treatment, exchangeable Ca2+ and Mg2+ were higher as compared to the CK treatment, showing urea could prevent leaching of exchangeable Ca2+ and Mg2+. Downward movement of exchangeable Ca2+ and Mg2+ was noticed in KCl treatment. In the multiple treatment, the downward movement of exchangeable Ca2+ and Mg2+ was evident, while that of K+ was less evident. Application of KNO3 strongly promoted the downward movement of exchangeable Ca2+ and Mg2+ in the soil profile.